12.18 __shsax intrinsic

This intrinsic inserts a SHSAX instruction into the instruction stream generated by the compiler.

It enables you to exchange the two halfwords of one operand, perform one signed 16-bit integer subtraction and one signed 16-bit addition, and halve the results.

Syntax

unsigned int __shsax(unsigned int val1, unsigned int val2)

Where:

val1

holds the first halfword operands

val2

holds the second halfword operands.

Return value

The __shsax intrinsic returns:

  • The halved addition of the low halfword in the first operand and the high halfword in the second operand, in the low halfword of the return value.

  • The halved subtraction of the low halfword in the second operand from the high halfword in the first operand, in the high halfword of the return value.

Examples

unsigned int exchange_subtract_add_halve(unsigned int val1, unsigned int val2)
{
    unsigned int res;
    res = __shsax(val1,val2); /* res[15:0] = (val1[15:0] + val2[31:16]) >> 1
                                 res[31:16] = (val1[31:16] - val2[15:0]) >> 1
                               */
    return res;
}
Related reference
10.147 ARMv6 SIMD intrinsics
Related information
SHSAX
ARM and Thumb instruction summary
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